The present invention relates to measurement and location apparatus. More particularly, the invention relates to multi-axis alignment apparatus for providing measurable angular information with respect to a ground plane.
Laser systems designed for a multitude of purposes have been generally commercially available since the 1960's. Basic refinements in these systems have included bulk reductions and the advent of the low power laser (with an output of the order of several milliwatts). With the compacting of laser technology, the number of practical laser applications have been compounded.
As compared to other conventional alignment techniques, the advantages of laser systems include increased sensitivity, faster recording of measurements and remote meter readout. These and other advantages have combined to provide impetus to an increasing trend toward the commercial use of lasers. In the field of manufacturing alignment techniques, laser devices are firmly embedded for applications such as aligning avionic systems on sophisticated aircraft. In this environment, the increased accuracy, decreased time required for alignment and the decrease in the necessary operator skill level all provide further incentives for employment of laser technology.
One reference pertaining to a type of optical measuring system is disclosed in U.S. Pat. No. 3,269,254, issued to L. Cooper et al. This device includes a graded mirror to define the roll, pitch and yaw orientation of a body to which the mirror is attached. The patentees use an autocollimation system to project the graded light pattern upon an image measuring reticle. A linear scale can be imposed upon the reticle for measuring angular displacement of the body. This scale is determinable based upon the distance of the collimating lens from the reticle and the focal length of the lens.
A fundamental problem with this type of configuration is that the collimator lens must be located close enough to the movable body to receive enough light rays to produce a discernable pattern at the reticle. The light source and reticle must also be displaced from the lens a distance no greater than its own focal length.
These and other inherent limitations restrict the Cooper system to a range of operation of about one to two feet between the movable body and imaging target, and to use with other than laser light sources. These are impractical limitations for the type of applications for which the present invention was intended. Nowhere has it been proposed that a purely electro-optical system may be employed to actually measure the degree of relative angular displacement between surfaces, in three axes, irrespective of the distance between the reference source and target.
In U.S. Pat. No. 3,701,602 of Bergin et al, a joint inventor of the present application, a diffraction device produces zero and first order beams from a single beam source. One or more of the beams is focussed by the diffraction device as with a spherical lens.
In U.S. Pat. No. 4,330,212 of Miller, a joint inventor of the present application, a single beam is broken up into a multiple of beams by a diffraction grating. Each known frequency of the ruling lines of the grating provides a known fixed angle between each diffracted order. The known fixed angle provides the measurement for any angular deviation from null.
The principal object of the invention is to provide new and improved alignment apparatus.
An object of the invention is to provide nongravity multi-axis alignment apparatus of simple structure, which is inexpensive in manufacture.
Another object of the invention is to provide single instrument apparatus utilizing a non-gravity reference to measure three-axis angular displacement of pitch, yaw and roll.
Still another object of the invention is to provide multi-axis alignment apparatus which is considerably less expensive in manufacture than the ST988 Roll Control Assembly and ST956 Tri-Axis Target and substantially eliminates polarization sensitivity, thereby permitting its use through intermediate glass elements, such as, for example, aircraft windshields.
Yet another object of the invention is to provide multi-axis alignment apparatus for boresighting military aircraft such as, for example, the Grumman A-6 and F-14 aircraft, with efficiency, effectiveness and reliability.
Another object of the invention is to provide multi-axis alignment apparatus for three-axis boresight control of all future aircraft and spacecraft with efficiency, effectiveness and reliability.
Still another object of the invention is to provide multi-axis alignment apparatus of simple structure, which is inexpensive in manufacture and is applicable to machine tool alignment for correcting angular errors in machine head or bed motion.
Yet another object of the invention is to provide multi-axis alignment apparatus which is readily adaptable to aligning precision guide rails in robotic systems or machinery centers, for example.